Socks used mostly for sports activities which have sections that differ from zone to zone in type of stitch and/or degree of elasticity are currently known. For example, U.S. Pat. No. 4,253,317 describes a short-legged sock for athletic use intended for the functions of compression and support of the arch, instep and ankle of the person wearing it. Such a sock comprises: a cuff; an upper imitation-ribbed part made by knitting an elastic thread with a basic thread; an instep-ankle section made with the said basic and elastic threads as in the upper part, but with the addition of internal terry loops of a certain prism density made with an additional thread; a heel section made without elastic thread, with the basic thread and with an additional thread for an internal terry stitch of another density; and a tip section which is knitted with the basic thread and a terry thread on the inside.
Therefore, only one elastic thread is used in the manufacture of such a sock in the upper-part and instep-ankle areas.
U.S. Pat. No. 4,397,161 also pertains to a short-legged sock having a leg section and a foot section, elasticized for a compression and a support function of the foot of the person wearing it. This sock is manufactured by knitting a basic thread and incorporating an elastomeric thread in the areas of the leg and of the foot with an elastomeric thread density greater in the foot section than in the leg section.
Therefore, only one elastic thread is used here as well, even though it has a density that is different from one part to another.
In addition, a so-called containment sock is known from U.S. Pat. No. 4,240,160 which can be used to keep the venous and lymphatic pressures at the ends of the lower limbs normal. However, the sock is produced by recutting a piece of elastic stitch and by sewing the recut outline in a direction and with a shaping that are suitable for making it possible for the sock to perform the function for which it has been provided.